Move Proxmox Container to Different Storage (Updated for LXC)

The Proxmox Web GUI does not give us the ability to migrate a container from one storage device to another directly. To move a container onto different storage we have to take a backup of the container and restore it to the same ID with a different storage device specified. This can be time laborious when working with several containers.

-d is specified if you would like the script to delete the temporary backup after the process has completed. Leave this out if you would like the backup tar file to be kept, just in case anything goes wrong.

-s is required to specify the name of the target storage. You can find this from the Proxmox Web GUI.

-c is required for the container ID to migrate.

In addition, the script contains the variable TMP. This will be the location of the backup tar created as part of the migration process and must contain enough space to store the content of the container being migrated. You can change this to suit your environment.

Proxmox backs up guests byte-for-byte in a compressed archive. Looking at LXC backups specifically, the file system is compressed into the target backup file with just a few exceptions – temp files aren’t included. You can also add your own exceptions by editing the vzdump.conf to exclude specific file patterns.

All that said, one of the biggest disk space wasters is the cache directory for apt which caches the installation packages for software you have installed. This can generally be safely removed on internet connected machines which will reduce your overall backup size.

For example, a newly created Debian LXC that’s been recently updated shows a total of 206MB of disk used.

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du-hs/var/cache/apt/

206M/var/cache/apt/

After clearing this with the command apt-get clean we can see the space has mostly been freed.

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apt-getclean

du-hs/var/cache/apt/

28K/var/cache/apt/

Considering this whole container is only consuming approximately 1GB of disk space, 200MB is quite significant.

vzdump hooks

Now we can see how much space we can save, we need to make Proxmox issue the apt-get clean command before it creates the backup of our container.

vzdump, the utility which Proxmox uses to perform backups has the ability to call a script for various stages of the backup process – these stages are:

backup-start

backup-end

backup-abort

log-end

pre-stop

pre-restart

post-restart

We can use these hooks to run our own commands at any of these points of the backup. For the goal of this blog post, we want to run the apt-get clean command at the point of backup-start.

Create a script on your Proxmox host with the following content:

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#!/bin/bash

if["$1"=="backup-start"]&&[${VMTYPE}=="lxc"];then

echo"Running pre backup guest cleanup for $3"

pct exec"$3"--bash-c"apt-get clean"

fi

Now edit your vzdump.conf file and add the following line to point to your new script. Remember to change the location of where your script is – I’ve just saved mine in /root/.

Renaming a Linux server’s hostname is usually a trivial task, and that’s no Different to a Proxmox server providing it’s not part of a cluster. If your machine is in a cluster then things get a bit more complicated and that’s a blog subject for another day.

For a single node machine it’s simple – Proxmox is Debian under the hood so simply follow the usual Debian process:

Change the hostname file to contain your new hostname

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vi/etc/hostname

To save having to restart, you can also run the hostname command to implement the change on a running machine. Otherwise you’ll need to reboot your server to pick up the change.

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hostname[NEW_HOSTNAME]

Next, edit your /etc/hostname file and change all occurrences of the old hostname with the new one.

Upgrade

Before updating, make sure all your VM’s have been stopped, both LXC and KVM. Ensure you have the required repository entries for apt. You’ll either need a valid license key or to add the less stable pve-no-subscription repository.

Proxmox has 2 API access points that can be used to control your Proxmox server and virtual guests. One of the API access points is using the command line, which you’re likely already familiar with. The other is the HTTP web API which is exposed as part of the WEB GUI on port 8006.

The Proxmox uses a JSON data format for returning data that can easily be parsed programmatically. Every command available to the pvesh command line command are available to the web based API as they share the same endpoint.

The endpoint for the Web API can be called using anything that can send and receive web based requests. We’ll use curl for the below examples. The endpoint to call would be similar to below – be sure you substitute yourip for the IP or hostname of your Proxmox server.

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https://yourip:8006/api2/json/

API Authentication

The next step is to authenticate your API requests with the Proxmox server. API authentication uses the same mechanism that logging into the Web GUI uses and requires a username, password and security realm.

Authentication is based on a token method which provides a ticket that must accompany all API requests except for the request that generates the token. A username and password will not be accepted for authentication with all other API requests. In addition, any requests that POST or write to the API endpoint must contain a CSRF Prevention Token.

To obtain an authentication token, run the below curl command and substitute your values as required – this example uses the root user and the default PAM realm.

The two interesting parts here are the ticket value and the CSRFPreventionToken and should be parsed out for use in later requests.

A token is valid for 2 hours and should be re-requested when it expires. Alternatively each request could generate it’s own token, however this generates added overhead.

List of Proxmox API Requests

pvesh is a command line utility can be used to perform the same actions as the web based API. You can, therefore, use the pvesh command to list all the possible API calls and navigate through the API call tree.

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# pvesh

entering PVE shell-type'help'forhelp

pve:/>

pve:/>ls

Dr---access

Dr---cluster

Dr---nodes

Dr-c-pools

Dr-c-storage

-r---version

pve:/>cdnodes

pve:/nodes>ls

Dr---prox-node1

You can then list the available commands from the root of the API using ls and then change into one of the child paths using cd. You can navigate throughout the whole API tree using these two methods to see what commands are available for calling. This is often the best way to get started with the Proxmox API.

Examples of API Requests

As stated earlier, all operations available in the Proxmox Web GUI can be performed through the API. Here are a few examples of API requests using Bash: